Adams, Brian

Bloomfield, John

Peach, Denis

Wheater, H.S.

NERC Open Research Archive

1 INTRODUCTION  Lowland catchments (<300m AOD) are subject to a complex set of environmental pressures and associ-ated management problems, and yet approaches to monitoring have generally been fragmented and un-dertaken on a reactive basis to operational problems. A strategic approach to monitoring is not yet the norm in most European countries at the river basin or even the catchment scale. As environmental awareness has grown, monitoring has increased in scope and breadth but has remained centred on fixed sampling-point and fixed time-interval sampling, of-ten with little interpretation of data. However, this is not just a European issue.  Worldwide, past monitoring efforts were not gen-erally able to provide early warning of: − The wide effects of eutrophication in the 1960s; − The effects of acidic deposition on water quality in the 1970s & 1980s; − The movement through soils and occurrence in groundwater and surface water of a range of pes-ticides in the 1970s & 1980s − The widespread occurrence of selenium in irriga-tion return waters in the western USA; − The impact of water abstractions on wetland habi-tats through into the 1990s; Furthermore, vast sums of money have been spent worldwide on treatment of municipal and in-dustrial wastewaters, reclamation of degraded rivers and wetlands and re-establishment of characteristic floral and faunal communities. However, in many cases the existing monitoring systems have not been able to provide the scientific evidence to judge whether the required or expected improvements in environmental status have been achieved. Whilst large sums of money have been spent on monitoring, policy and management results are often lacking.  This situation illustrates the difficulty of collect-ing, interpreting and using data adequately to ad-dress a range of objectives and issues which may as yet not be apparent. A truly comprehensive assess-ment system must address the current, known water issues and provide background information neces-sary for the early detection of future changes in sur-face and groundwater status (and the associated im-pacts on the environment) from whatever causes. This paper describes a unique initiative being un-dertaken in the UK to gain improved understanding of the hydrological cycle at the meso-catchment scale. The Lowland CaProposed European legislation (The Water Framework Directive) requires establishment and maintenance of good ecological, quantitative and qualitative status of surface waters and good quanti-tative and qualitative status of groundwaters. It is ev-ident that any human intervention in the hydrologi-cal cycle (e.g. groundwater abstraction, changes of land use, introduction of treated sewage into surface waters) will have an impact on the extant status of surface and/or groundwaters. To be able to predict the impact that such interventions will have and also tchment Research programme (LOCAR) will focus on two pairs of catchments on the Chalk (England’s prime aquifer in terms of pub-lic water supply) and one catchment on Permo-Triassic sandstone (England’s second most im-portant aquifer), see Figure 1.  Support for Integrated Groundwater / Surface water Monitoring and Assessment for Sustainable Catchment Management  D.W.Peach, B.Adams and J.P.Bloomfield British Geological Survey, Wallingford, United Kingdom H.Wheater Imperial College of Science, Technology and Medicine, London, United Kingdom  ABSTRACT: Sustainable management of groundwater at the catchment scale requires conceptual and possi-bly subsequent numerical and/or analytical models to be developed. These depend on an understanding of the key hydrological, hydrogeological and geomorphological process interactions. Recent initiatives have indicat-ed: 1) a shortage of the basic data relating to these processes, 2) uncertainty as to what additional data may be required, how and where to collect them. A new research initiative will develop and test methodologies to produce guidelines for monitoring and assessment at the catchment scale. This will be achieved by addressing key scientific and technical issues in a series of carefully instrumented lowland permeable catchments. to be able to plan measures to recover “good status” has implications for data requirements and also the degree to which the processes involved are under-stood. Figure 1. Locations of the LOCAR research catch-ments  In addition, the perceived impacts of future cli-mate change have important implications for water resources management. In the south and east of the United Kingdom winters are expected to be wetter (with generally more intense storm events) and summers drier whilst in the north-west rainfall is ex-pected to increase throughout the year. There is evi-dence to suggest an amplification of the current monthly distribution of both rainfall and runoff through the year (Marsh 1996). However, the precise response of catchments depends on the current cli-mate, catchment geology and land use. Recent plans announced by the UK’s Department of the Environment, Transport and the Regions (DETR) indicate that some 4 million new homes will be required by 2016 in the South of England to meet the predicted future demand for housing. This will inevitably put a much greater demand on water resources in this part of the country – an area where groundwater currently provides up to 80% of public water supply. 2 THE LOCAR PROGRAMME The lack of an integrated science base for lowland catchments has been recognised in a number of re-cent national and European reviews within the water sector (e.g. Acreman & Adams 1998, European Commission 1998, Dept. of Environment 1996, Grey et al. 1995). There is limited understanding of the underlying surface and subsurface hydrological processes and their interactions, the effects of land-use change on water, sediment and solute fluxes, the associated transport and degradation of contami-nants, the hydrological controls on ecological sys-tems (in particular with respect to aquatic, riparian and wetland habitats), and the effects of climatic variability. Integrated models are required to provide a focus for integrated science and to combine under-standing of process interactions for predictive stud-ies. The LOCAR programme will address the fol-lowing issues: 1 What are the key hydrological processes control-ling surface water-groundwater interactions and the movement of groundwater in lowland catch-ments? 2 What are the key physical, chemical and biologi-cal processes operating within the valley floor corridor which affect the surface water and groundwater? 3 How do the varying flow regimes control in-stream, riparian and wetland habitats? 4 How does land use management impact on low-land catchment hydrology, including both water quantity and quality? 5 How can the hydrological, hydrogeological, geo-morphological and ecological interactions result-ing from natural or anthropogenic changes be predicted using integrated mathematical models? The long term results from the five-year research programme will include improved characterisation of subsurface flow and transport processes. It will also provide improved knowledge of the impacts of land use, better understanding of the hydrological controls on stream and wetland ecology, and new holistic methods to evaluate the impacts of natural and anthropogenic change on lowland catchment systems. The meso-scale (200-500 km2) catchments were chosen to encompass the two main aquifers in UK, the Cretaceous Chalk and Permo-Triassic sandstones and on the basis of availability of data. A review of existing hydrological, hydrogeologi-cal and ecological data for the three catchments was carried out (Peach 2000). In spite of the relatively large amount of previous work that had been carried out in these catchments there was still a significant lack of knowledge on various aspects of, for exam-ple, the hydrogeology. In the Pang catchment there is uncertainty over both the location of a groundwa-ter divide and the importance of karstic groundwater flow in the Chalk below Palaeogene cover. Whilst the local geology is fundamental to understanding the hydrogeology, some parts of these catchments were last mapped some 70 or more years ago and geological models and mapping techniques have changed significantly since then (Bristow et al. 1998). In summary, results of the review indicated a great variability of data availability, both in type and space, e.g. good monitoring of groundwater in part Tern catchmentLambourn  and Pang catchmentFrome and Piddle catchmentof one catchment, no automatic weather stations on any catchment, very patchy ecological information, basic conceptual models based on very incomplete knowledge of processes or even groundwater catch-ment size/boundaries, poorly understood geology and no integration of monitoring systems between groundwater, surface water, ecological and meteoro-logical measurements. From a groundwater perspective the knowledge that is required to develop a quantified conceptuali-sation of a groundwater catchment and its behaviour encompasses: - geological and hydrogeological boundaries, physical structure of the aquifer(s), re-charge, discharge, groundwater flow patterns and mechanisms, rock-groundwater interactions and ef-fects of the unsaturated zone. Both catchment scale and local scale monitoring is inadequate to serve the research needs of the LOCAR programme.  It was clear therefore that monitoring instrumentation would need to be in-stalled to assist in the evaluation of: 1 Definition of groundwater catchment boundaries, 2 Determination of recharge processes in the inter-fluve areas, 3 Definition of three-dimensional groundwater flow across the catchment, 4 Characterisation of fracture flow, 5 Evaluation of heterogeneity and scaling effects, 6 Determination of the mechanisms of groundwa-ter-surface water interaction near discharge points. The monitoring infrastructure proposed seeks to achieve these aims by: 1 The augmentation of the existing monitoring networks in order to achieve a minimum standard of baseline monitoring e.g. by the installation of additional boreholes, rain gauges, fish counters, flow gauges etc. 2 The establishment of individual monitored facili-ties to enable research into particular aspects of catchment processes e.g. wetlands, surface wa-ter/groundwater interaction, fissure flow and re-charge (Figure 2), and one off surveys of ecology, hydrology (incremental flows) and geology (re-vised mapping including Drift cover where pre-sent).  Broad consultation with the research community over several field trips and full day workshops demonstrated the difficulties of defining “baseline” monitoring.  Inevitably, budgetary constraints rather than scientific research requirement determined the final extent of the planned monitoring networks. Ini-tial cost estimates for instrumentation and works to provide these facilities amounted to approximately £6.7M (approx. US$10M). In order to retain a pro-portion of the £9.75M overall budget for the scien-tific research programme a revision down to about £4M was necessary. A further £1M will be required for management of the catchment over the 5 years of the programme. In summary, the proposed infrastructure was costed at £5 million (to include specification/design and installation of equipment/facilities, supervision of the installation, project management monitoring activities and project management). A sum of some £4.75 remains for the 5-year research programme, for which integrated research proposals will be in-vited from within the scientific community. 3 CONCLUSIONS In order to achieve the aims of the LOCAR pro-gramme two pairs of Chalk catchments and one Permo-Triassic sandstone catchment have been cho-sen and reviewed for the design and installation of an upgraded monitoring system. In spite of the knowledge base relating to these catchments the re-view showed that current monitoring systems were not adequate to provide baseline hydrological, hy-drogeological, meteorological or ecological data to address the environmental, scientific and manage-ment issues. Significant investment is required to provide a minimum standard of baseline data to ena-ble researchers to improve our understanding of the catchment processes occurring. The need for this in-vestment in basic infrastructure is indicative of the responsive, rather than strategic, approach to moni-toring that is not uncommon throughout Europe. The LOCAR programme is designed to enhance under-standing of the processes occurring within lowland permeable catchments through a programme of inte-grated monitoring and research initiatives. This in turn will enable optimisation of future strategic mon-itoring programmes. This paper is published by permission of the Di-rector BGS (NERC). 4 REFERENCES Acreman, M.C. & Adams, B. 1998. Low flows, groundwater and wetland interactions – a scoping study. Report to the Environment Agency (W6-013), UKWIR (98/WR/09/1) and NERC (BGS WD/98/11) Bristow, B., Mortimore, R. & Wood, C. 1998. Lithostratigraphy for mapping the Chalk of south-ern England. Proc. Geologists’ Association. 109: 293-315. Department of the Environment and Welsh Office. 1996. Water resources and supply: Agenda for ac-tion. HMSO London. European Commission, JRC-DGXII. 1998. Freshwa-ter, a challenge for research and innovation – a concerted European response. Environment-Water Task Force EUR 18098 EN. Grey, D.R.C., Kinninburgh, D.G., Barker, J.A. & Bloomfield, J.P. 1995. Groundwater in the U.K. A strategic study. Issues and research needs. Groundwater Forum Report FR/GF 1. Marsh, T.J. 1996. The 1995 U.K. drought – a signal of climate instability? Proc. Instn. Civ. Engrs. Wat., Marit., & Energy. 118, pp 189-195. Peach, D. (Editor) 2000. Proposals for infrastructure and monitoring on the LOCAR catchments. Un-published report to Natural Environment Re-search Council. pp114. Figure 2. Proposed instrumentation at recharge investigation sites in the LOCAR programme (Peach, 2000) Equitensiometer to 10m at 1m intervals Deep tensiometerPuncture tensiometers at 10cm intervals to 1m4m access tubesNeutron probeTowerSoil water suction samplesHydra evaporation sensorAutomatic weather stationSolar radiationNet radiationWind directionWind speedTemperature and humidityRain gaugeBore HoleTipping bucket recorder30 - 50 m access tube (experimental)9 m access tube Plastic sheetNet rainfall gauges

Support for integrated groundwater/surface water monitoring and assessment for sustainable catchment management

http://nora.nerc.ac.uk/18619/1/Peach%20et%20al%202000%20Cape%20Town%20IAH.pdf

Support for integrated groundwater/surface water monitoring and assessment for sustainable catchment management

Abstract

Similar works

Full text

Available Versions

NERC Open Research Archive